internal/lockedfile: optionally force write lock

For acquiring a write lock on a directory.

Signed-off-by: Ophestra <cat@gensokyo.uk>

3 files changed, 20 insertions, 7 deletions

diff --git a/internal/lockedfile/lockedfile.go b/internal/lockedfile/lockedfile.go
index f48124ff..c7baff60 100644
--- a/internal/lockedfile/lockedfile.go
+++ b/internal/lockedfile/lockedfile.go
@@ -34,15 +34,12 @@ type osFile struct {
 	*os.File
 }
 
-// OpenFile is like os.OpenFile, but returns a locked file.
-// If flag includes os.O_WRONLY or os.O_RDWR, the file is write-locked;
-// otherwise, it is read-locked.
-func OpenFile(name string, flag int, perm fs.FileMode) (*File, error) {
+func openFile(name string, flag int, perm fs.FileMode, w bool) (*File, error) {
 	var (
 		f   = new(File)
 		err error
 	)
-	f.osFile.File, err = openFile(name, flag, perm)
+	f.osFile.File, err = osOpenFile(name, flag, perm, w)
 	if err != nil {
 		return nil, err
 	}
@@ -59,11 +56,23 @@ func OpenFile(name string, flag int, perm fs.FileMode) (*File, error) {
 	return f, nil
 }
 
+// OpenFile is like os.OpenFile, but returns a locked file.
+// If flag includes os.O_WRONLY or os.O_RDWR, the file is write-locked;
+// otherwise, it is read-locked.
+func OpenFile(name string, flag int, perm fs.FileMode) (*File, error) {
+	return openFile(name, flag, perm, false)
+}
+
 // Open is like os.Open, but returns a read-locked file.
 func Open(name string) (*File, error) {
 	return OpenFile(name, os.O_RDONLY, 0)
 }
 
+// OpenDir is like Open, but returns a write-locked directory.
+func OpenDir(name string) (*File, error) {
+	return openFile(name, os.O_RDONLY, 0, true)
+}
+
 // Create is like os.Create, but returns a write-locked file.
 func Create(name string) (*File, error) {
 	return OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
diff --git a/internal/lockedfile/lockedfile_filelock.go b/internal/lockedfile/lockedfile_filelock.go
index 9fc16a9b..1f5ca310 100644
--- a/internal/lockedfile/lockedfile_filelock.go
+++ b/internal/lockedfile/lockedfile_filelock.go
@@ -13,7 +13,7 @@ import (
 	"hakurei.app/internal/lockedfile/internal/filelock"
 )
 
-func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
+func osOpenFile(name string, flag int, perm fs.FileMode, w bool) (*os.File, error) {
 	// On BSD systems, we could add the O_SHLOCK or O_EXLOCK flag to the OpenFile
 	// call instead of locking separately, but we have to support separate locking
 	// calls for Linux and Windows anyway, so it's simpler to use that approach
@@ -24,6 +24,10 @@ func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
 		return nil, err
 	}
 
+	if w {
+		flag |= os.O_WRONLY
+	}
+
 	switch flag & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR) {
 	case os.O_WRONLY, os.O_RDWR:
 		err = filelock.Lock(f)
diff --git a/internal/lockedfile/lockedfile_plan9.go b/internal/lockedfile/lockedfile_plan9.go
index a2ce794b..45e2b87c 100644
--- a/internal/lockedfile/lockedfile_plan9.go
+++ b/internal/lockedfile/lockedfile_plan9.go
@@ -42,7 +42,7 @@ func isLocked(err error) bool {
 	return false
 }
 
-func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
+func osOpenFile(name string, flag int, perm fs.FileMode, _ bool) (*os.File, error) {
 	// Plan 9 uses a mode bit instead of explicit lock/unlock syscalls.
 	//
 	// Per http://man.cat-v.org/plan_9/5/stat: “Exclusive use files may be open